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Sewerage Vent West Perth

One of the more curious heritage structures in Perth is a series of sewerage vents which have been entered in the State Register of Heritage Places. Each vent is similar in design, comprising an ornate circular cast iron base with fluting and moulding which contains the letters MS, for Metropolitan Sewerage, in the lower portion.

As the sewerage system expanded in the late 19th and early 20th centuries, complaints of foul odours began to emerge, particularly in summer. The smell of sewage worried residents not only for its obnoxiousness, but because it was believed to be a cause of disease. As well as being smelly, hydrogen sulphide is highly corrosive, so ventilating sewerage systems is important for the piping as well as residents. The way to deal with this is to install tall ventilating shafts at key points, so the gas can be released high enough in the air for the wind to take it away.

It is not clear why every vent was constructed where they were placed, but it seems likely that one reason was where the distance between houses was too great, as the residential connections themselves provided some ventilation. Or they may simply have been installed in response to complaints about the odours in an area.

It is also uncertain when these vents were disconnected from the sewer system. As areas were redeveloped, many vents were removed, but those that remain are a reminder of the importance of the sewerage system in a city, something most people do not think about.

Detailed Description

One of the more curious heritage structures in Perth is a series of sewerage vents which have been entered in the State Register of Heritage Places. Each vent is similar in design, comprising an ornate circular cast iron base with fluting and moulding which contains the letters MS, for Metropolitan Sewerage, in the lower portion.

As the sewerage system expanded in the late 19th and early 20th centuries, complaints of foul odours began to emerge, particularly in summer. The smell of sewage worried residents not only for its obnoxiousness, but because it was believed to be a cause of disease. Many of these complaints related to the Claisebrook and Burswood treatment works, with the river near the sewerage works reported as stinking much of the time.

Noxious odours in sewerage are caused by hydrogen sulphide, which the human nose can detect in very small quantities in the air. The main source of hydrogen sulphide in sewerage systems is the slime that builds up on sewer walls, not the flow of fresh sewage. As well as being smelly, hydrogen sulphide is highly corrosive, so ventilating sewerage systems is important for the piping as well as residents. The way to deal with this is to install tall ventilating shafts at key points, so the gas can be released high enough in the air for the wind to take it away.

In December 1911, the Metropolitan Water Supply Sewerage and Drainage Department (MWSS&DD) told Perth City Council it was going to erect a ventilating shaft at Cook Street. It was to be “a cast iron base and the usual standard pattern for streets”. Another such vent was to be constructed at Adelaide Terrace near the corner of Victoria Square. The reference to the usual standard pattern suggests these two were not the first vents. The Adelaide Terrace vent was a response to complaints from locals, so it is likely the Cook Street vent was also because of foul smells noticed by residents.

It is not clear why every vent was constructed where they were placed, but it seems likely that one reason was where the distance between houses was too great, as the residential connections themselves provided some ventilation. Or they may simply have been installed in response to complaints about the odours in an area.

It is also uncertain when these vents were disconnected from the sewer system. It has been suggested that, after World War II, changes in the way the sewerage system was operated meant there was no longer a need for ventilation. Or they may have simply become redundant after the conversion to a closed sewer system in the 1970s. The shift to plastic piping, which suffers less from the corrosive effects of hydrogen sulphide, also meant there was less need to have the system ventilated.

As areas were redeveloped, many vents were removed, but those that remain are a reminder of the importance of the sewerage system in a city, something most people do not think about.